Electronic Fuel Injection
ELECTRONIC PETROL INJECTION
ELECTRONIC PETROL INJECTION
The motor industry is trying to continue to reduce fuel emissions with no loss in
performance.
This had become more and more difficult with carburettors, they had become very
complex and expensive. The alternative has been petrol injection, petrol injection
will deliver the exact amount of fuel for all engine speeds and loads.
Fuel is injected directly onto the inlet valve,(multi-point systems) therefore only air
will flow in the inlet manifold and fuel pressure is kept low making component cost
less than those found with diesel injection.
TYPES OF SYSTEMS
Based on Bosch
K JETRONIC
KE JETRONIC
Mechanical continuous injection
Electronic mechanical continuous injection
The following systems operate their injectors intermittently all at once
D JETRONIC
Pressure sensing “Druck” (pressure)
L,LE,LU,L3 JETRONIC Air flow sensing “Luft” (air)
LH JETRONIC
Hot wire measurement of air mass
MOTRONIC
Fuel and ignition management
MONO JETRONIC
Single point injection
SEQUENTIAL FUEL INJECTION
Injectors operate in the firing order
Injector is switched off
Injector
Intake manifold
Inlet valve
Injector switched on
Fuel is being delivered
on top of the inlet valve.
FUEL PUMP
+
The roller cell pump is driven by a permanently
magnetic electric motor. The periphery of the
rotating eccentric rotor plate has pocket shaped
openings, in each of which there is a metal roller.
Centrifugal force will move the rollers out, so that
they function as a circulating seal . The pumping
action is introduced by periodically increasing the volume of the fuel feed and/or by
reducing the volume of the output. A safety valve will connect the pressure and suction
ends when there is an abnormal increase in pressure. A check valve in the pressure
connection provides the necessary supply pressure for when the engine is restarted from
hot. The valve will close when the engine is turned off.
FUEL PUMP
+
10
11
-
1 2
3
9
PLEASE NAME THE PARTS
OF THE FUEL PUMP
4
5
6
7
8
FUEL PUMP
+
-
Fuel pump switched off
FUEL PUMP
+
Check
valve open
-
Fuel pump is now operating,
fuel is passing through the
pump causing the check valve
to open thus allowing fuel
pressure into the system.
FUEL PUMP
+
-
Safety valve has opened
System
Restriction
Please note, if there is a
restriction in the system, a
safety valve at the suction
end of the pump will open,
thus causing a pressure drop
in the pump.
FUEL PUMP
+
-
Pump has now been switch off.
INJECTION SYSTEM WIRING LAYOUT
Please complete the following wires into
your work book, along with component names.
Fuel pump Fuse
Control relay
87
ECU
M
87b
50
1
31
1
15
4
30
-
+
1
15
Ignition
module
COOLANT
SENSOR
AIR
THROTTLE AIR FLOW
VALVE SWITCH
FLOW METER
COLD START THERMO-TIME
VALVE
SWITCH
Ignition
switch
INJECTORS
BATTERY
FUEL PRESSURE TEST
1. Disconnect the fuel supply to the fuel rail.
2. Connect pressure gauge to high pressure fuel line.
3. Start the engine and note the reading in bar.
2 to 3 bar multi-point injection systems
1 to 1.5 bar single point injection systems
4. Disconnect the vacuum pipe to the pressure and record the reading
in bar. Note! this does not apply to systems with fuel fuel
pressure regulators not fitted with vacuum pipes.
2
1
0
3
4
Fuel pressure gauge
Reading.............bar
Reading now with
Vacuum pipe removed
........................bar
FUEL PUMP DELIVERY RATE
2
1
0
3
4
1. Disconnect fuel return pipe from the fuel pressure regulator.
2. Connect in it’s place a pipe and direct the pipe into a measuring
vessel.
3. Remove the fuel pump relay.
4. Connect across ‘terms’ 30/88 and 87 a jump wire.
5. Switch on the ignition and operate the fuel pump for 15 seconds
pto
2
1
0
3
4
6. Record the reading for 15 seconds......................
EXAMPLE 540 cm
0.5 Ltr
19 fl oz
VIBRATION DAMPER
VIBRATION DAMPER
Please identify the following parts
2
1
1
3
4
5
6
Because of pressure variations in the fuel system, a pulsation damper is fitted into the
fuel line between the fuel pump and the fuel filter. This reduces noise resulting in
pressure variations created by the injectors and pressure regulator.
FUEL FILTER
FUEL FILTER
The filter has an arrow on it,s body, this indicates the way it is
fitted to the fuel system. The arrow shows direction of flow from
the fuel tank.
FUEL FILTER
Please identify
parts of the filter.
1
2 3
Paper cartridge with a seperation mesh of 8 to 10 Micron and a
surface area of 3000cm squared.
The direction of flow is shown by the arrows
FUEL PRESSURE REGULATOR
The fuel pressure regulator keeps the fuel pressure constant,
regardless of the delivery and ejected volume of fuel.
The excessive fuel will flow back to the tank via a return line,
so that there will be cool and vapor lock free fuel for the injection
valves.
FUEL PRESSURE REGULATOR
Rest position
From fuel
rail
To fuel tank
Valve
Diaphragm
Spring
Vacuum
The spring will control the pressure of the system, when the
fuel pressure increases the it will exert a downward force on the
diaphragm, thus opening the return valve to the tank. AS SEEN ON
THE NEXT SCREEN
Regulator has opened due
to an increase in pressure.
The regulator will continue
to open and close, to
regulate system pressure
From fuel
rail
To fuel tank
Valve
Diaphragm
Spring
Vacuum
To fuel tank
From fuel
rail
Valve
Diaphragm
Spring
Vacuum
Purpose of the vacuum
connection
From fuel
rail
To fuel tank
Valve
Diaphragm
Spring
Vacuum
The spring chamber of the pressure regulator is connected with the Plenum chamber by
way of a hose. In this manner the fuel pressure 2.5 + or - 0.2 bar will be influenced to a
degree depending on the intake manifold depression.
The difference between injection pressure and intake pressure will always remain constant
and the volume of fuel injected from the injection valves will only depend on opening
period.
NOTE THE OPERATION ON THE NEXT SCREENS
The engine is at idle
producing a high manifold
depression.
From fuel
rail
To fuel tank
Valve
Diaphragm
Spring
AIR SUPPLY
TO THE ENGINE
High Vacuum
MANIFOLD DEPRESSION
Throttle has been
opened and the
manifold depression
has reduced
From fuel
rail
To fuel tank
Valve
Diaphragm
Spring
Low Vacuum
FUEL PRESSURE REGULATOR TEST
1. Disconnect vacuum pipe from pressure regulator.
2. Remove fuel pump relay and fit by pass cable.
3. Record fuel pressure...............bar
FUEL PRESSURE REGULATOR TEST
vacuum pump
4. Connect a vacuum pump to the pressure regulator.
5. Apply a vacuum of 0.5 bar.
6. Record fuel pressure.................bar
NOTE Pressure should drop by about 0.5 bar.
7. turn off the fuel pump, pressure should hold.
TICK BOX
Yes [
]
No [ ]
FUEL INJECTOR
FUEL INJECTOR
7
6
5
4
3
2
1
An electro magnetic injection valve (or fuel injector) is located in the intake port
immediately in front of the intake valve of each cylinder.
These injection valves are connected parallel and inject fuel simultaneously once for each
turn of the crankshaft.
FUEL INJECTOR
Injector in the off position
FUEL INJECTOR
Injector is switch on
If the magnet is excited and the nozzle needle is lifted off of it’s seat by approx. 0.15mm,
the fuel can be let out through the calibrated annular gap at the existing pressure. The
fine atomization is caused by a ground spraying pintle at the front end of the nozzle needle.
The lifting and dropping times of the valve are less than 1ms; the opening time between
2 and 10ms.
FUEL INJECTOR
Injector has now been switched off
INJECTION SYSTEM WIRING LAYOUT
Please complete the following wires into
your work book, along with component names.
Fuel pump Fuse
Control relay
87
ECU
M
87b
50
1
31
1
15
4
30
-
+
1
15
12
13
Ignition
module
COOLANT
SENSOR
AIR
THROTTLE AIR FLOW
VALVE SWITCH
FLOW METER
COLD START THERMO-TIME
VALVE
SWITCH
Ignition
switch
INJECTORS
BATTERY
INJECTOR TEST
Injector
OHMS
FUEL INJECTOR
FUEL INJECTOR PULSE TIMES
ENGINE COLD
ms
%
Degrees
Cranking
4+
6.66+
3.99+
Idle
4
6.66+
3.99
Cranking
2.2+
3.74+
2.25+
Idle
2.5
3.74
2.24
1000 rpm
2.4
4
2.40
2000 rpm
2.3
7.66
4.59
3000 rpm
2.2
11.00
6.60
Snap open throttle
6+
20+
12+
ENGINE WARM
INJECTOR SCOPE PATTERN
A
B
C
Please can you identify what is happening to the injector at A, B, and C
FUEL INJECTOR DELIVERY TEST
Position the injection valves over a suitable containers .
Briefly operate the starter motor and check that an even cone shaped
spray is delivered from each injector.
FUEL INJECTOR DELIVERY TEST
A
B
C
D
A, B, and D are correct C is not acceptable as it is more than
10% greater in delivery.
FUEL INJECTOR LEAK RATE TEST
With the injector valves positioned over the containers.
Turn on the ignition for 5 seconds. No more than 2 drops of fuel
per minute should leak from each injector.
FUEL INJECTOR WIRING TEST USING A TEST LAMP
COLD START INJECTOR
COLD START INJECTOR CIRCUIT
Only operates during cranking when the engine is cold for a period of up to 8 seconds.
The injector gets it,s earth through the thermal timeswitch. Inside of the switch is a bi-metal strip and heater
coil. When the injector is operated during cranking the
heater coil heats the bi-metal strip which will bend and
break the earth of the cold start valve.